This website uses cookies to deliver some of our products and services as well as for analytics and to provide you a more personalized experience. Click here to learn more. By continuing to use this site, you agree to our use of cookies. We've also updated our Privacy Notice. Click here to see what's new.

This website uses cookies to deliver some of our products and services as well as for analytics and to provide you a more personalized experience. Click here to learn more. By continuing to use this site, you agree to our use of cookies. We've also updated our Privacy Notice. Click here to see what's new.

About Optics & Photonics TopicsOSA Publishing developed the Optics and Photonics Topics to help organize its diverse content more accurately by topic area. This topic browser contains over 2400 terms and is organized in a three-level hierarchy. Read more.

Topics can be refined further in the search results. The Topic facet will reveal the high-level topics associated with the articles returned in the search results.

Abstract

We study the linear polarization of the emission from single quantum dots embedded in an “L3” defect nanocavity in a two-dimensional photonic crystal. By using narrow linewidth optical excitation in resonance with higher-order modes, we are able to achieve strong quantum dot emission intensity whilst reducing the background from quantum dots in the surrounding lattice. We find that all the dots observed emit very strongly linearly polarized light of the same orientation as the closest mode, despite the fact that these quantum dots may be spectrally detuned by several times the mode linewidth. We discuss the coupling mechanisms which may explain this behavior.

Figures (4)

Fig. 1. (a) Photoluminescence spectra of Cavity A taken at high excitation power with non-resonant excitation, detecting linear polarization along x (red) and along y (blue) to the Γ-K photonic lattice axis. The grey spectrum shows the ensemble QD PL emission on an unpatterned part of the wafer. (b) Polar PL intensity plots of modes M1–M3, M5. x (y) corresponds to 0° (90°) relative to the defect axis. Modes are labelled according to their parity along the x (upper labels) and y axes (lower labels), as described in ref [9]. (c) |E|2 mode patterns for modes 1–3 and 5 for Cavity A calculated using the guided-mode expansion method [9,15,16].

Fig. 2. (a) Multichannel photoluminescence excitation (PLE) spectra of Cavity A. The excitation power is kept such that both the mode and several QD features are observed, and the wavelength of the exciting laser stepped from 886nm (below the wavelength of Mode 5) to 905nm (above the wavelength of Mode 5). A spectrum is taken at each step. The spectra are shifted both vertically and horizontally for clarity. (b) Spectrum around Mode 3 taken for the excitation wavelength which gives maximum intensity (indicated in red in (a)). (c) Normalized intensity of Mode 3 (green squares), QD 1 (blue open circles), QD 2 (black open diamonds) as a function of excitation wavelength (PLE spectra). The spectral positions of these features are shown in (b). The PL of Mode 5 (red) taken from Fig 1(a) is also shown for comparison.

Fig. 3. (a) PL emission from Cavity A at Mode 3, taken for excitation with a CW Ti:sapphire laser tuned to be resonant with the wavelength of Mode 5. Blue shows excitation polarization co-linear with the polarization of Mode 5 (along y), red for opposite linear polarization (along x). The excitation power was chosen to be strong enough that the Mode 3 emission dominates over single QD features. The detection polarization was chosen to match that of Mode 3 (along x). (b) PL spectrum around Mode 3 at lower excitation intensity, showing both QD and mode features. The excitation polarization was kept along y, with the detection polarization along y (blue) or along x (red). (c) Linear polarization, defined as ρ=[I(x)-I(y)]/[I(x)+I(y)] of single QD features from (b). The dashed line indicates the polarization of Mode 3 at high power.

Fig. 4. (a) Photoluminescence spectra of Cavity B. The broad feature observed corresponds to the fundamental mode, and the sharp features to single QD lines. The PL is detected co-polarized (y - blue) and cross-polarized (x - red) to the mode. (b) Polarization of the mode and single QD lines observed over this spectral range. Positive polarization is along the y-direction. (c) PL spectra taken for increasing temperature, showing the mode and QD2 on the long wavelength side only. (d) Polarization of mode (blue) and QD (red) as a function of temperature.